State of the art broadcast encryption methods are described in the following publications, the disclosures of which are hereby incorporated by reference:    A. Fiat and M. Naor, Broadcast Encryption, Advances in Cryptology—CRYPTO '93 Proceedings, Lecture Notes in Computer Science, Vol. 773, 1994, pp. 480-491.    NIST. FIPS-197: Advanced Encryption Standard.            http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf.            S. Frankel. AES-XCBC-MAC-96 Algorithm And Its Use With IPSec.            http://www.ietforg/rfc/rfc3566.txt            NIST. FIPS-81: DES Modes Of Operation.            http://www.itl.nist.gov/fipspubs/fip81.htm            H. Krawzyk. RFC 2104—Keyed-Hashing for Message Authentication.            http://www.faqs.org/rfcs/rfc2104.html            NIST. FIPS 180-1: Secure Hash Standard.